1perf-record(1) 2============== 3 4NAME 5---- 6perf-record - Run a command and record its profile into perf.data 7 8SYNOPSIS 9-------- 10[verse] 11'perf record' [-e <EVENT> | --event=EVENT] [-a] <command> 12'perf record' [-e <EVENT> | --event=EVENT] [-a] \-- <command> [<options>] 13 14DESCRIPTION 15----------- 16This command runs a command and gathers a performance counter profile 17from it, into perf.data - without displaying anything. 18 19This file can then be inspected later on, using 'perf report'. 20 21 22OPTIONS 23------- 24<command>...:: 25 Any command you can specify in a shell. 26 27-e:: 28--event=:: 29 Select the PMU event. Selection can be: 30 31 - a symbolic event name (use 'perf list' to list all events) 32 33 - a raw PMU event (eventsel+umask) in the form of rNNN where NNN is a 34 hexadecimal event descriptor. 35 36 - a symbolic or raw PMU event followed by an optional colon 37 and a list of event modifiers, e.g., cpu-cycles:p. See the 38 linkperf:perf-list[1] man page for details on event modifiers. 39 40 - a symbolically formed PMU event like 'pmu/param1=0x3,param2/' where 41 'param1', 'param2', etc are defined as formats for the PMU in 42 /sys/bus/event_source/devices/<pmu>/format/*. 43 44 - a symbolically formed event like 'pmu/config=M,config1=N,config3=K/' 45 46 where M, N, K are numbers (in decimal, hex, octal format). Acceptable 47 values for each of 'config', 'config1' and 'config2' are defined by 48 corresponding entries in /sys/bus/event_source/devices/<pmu>/format/* 49 param1 and param2 are defined as formats for the PMU in: 50 /sys/bus/event_source/devices/<pmu>/format/* 51 52 There are also some parameters which are not defined in .../<pmu>/format/*. 53 These params can be used to overload default config values per event. 54 Here are some common parameters: 55 - 'period': Set event sampling period 56 - 'freq': Set event sampling frequency 57 - 'time': Disable/enable time stamping. Acceptable values are 1 for 58 enabling time stamping. 0 for disabling time stamping. 59 The default is 1. 60 - 'call-graph': Disable/enable callgraph. Acceptable str are "fp" for 61 FP mode, "dwarf" for DWARF mode, "lbr" for LBR mode and 62 "no" for disable callgraph. 63 - 'stack-size': user stack size for dwarf mode 64 - 'name' : User defined event name. Single quotes (') may be used to 65 escape symbols in the name from parsing by shell and tool 66 like this: name=\'CPU_CLK_UNHALTED.THREAD:cmask=0x1\'. 67 - 'aux-output': Generate AUX records instead of events. This requires 68 that an AUX area event is also provided. 69 - 'aux-sample-size': Set sample size for AUX area sampling. If the 70 '--aux-sample' option has been used, set aux-sample-size=0 to disable 71 AUX area sampling for the event. 72 73 See the linkperf:perf-list[1] man page for more parameters. 74 75 Note: If user explicitly sets options which conflict with the params, 76 the value set by the parameters will be overridden. 77 78 Also not defined in .../<pmu>/format/* are PMU driver specific 79 configuration parameters. Any configuration parameter preceded by 80 the letter '@' is not interpreted in user space and sent down directly 81 to the PMU driver. For example: 82 83 perf record -e some_event/@cfg1,@cfg2=config/ ... 84 85 will see 'cfg1' and 'cfg2=config' pushed to the PMU driver associated 86 with the event for further processing. There is no restriction on 87 what the configuration parameters are, as long as their semantic is 88 understood and supported by the PMU driver. 89 90 - a hardware breakpoint event in the form of '\mem:addr[/len][:access]' 91 where addr is the address in memory you want to break in. 92 Access is the memory access type (read, write, execute) it can 93 be passed as follows: '\mem:addr[:[r][w][x]]'. len is the range, 94 number of bytes from specified addr, which the breakpoint will cover. 95 If you want to profile read-write accesses in 0x1000, just set 96 'mem:0x1000:rw'. 97 If you want to profile write accesses in [0x1000~1008), just set 98 'mem:0x1000/8:w'. 99 100 - a BPF source file (ending in .c) or a precompiled object file (ending 101 in .o) selects one or more BPF events. 102 The BPF program can attach to various perf events based on the ELF section 103 names. 104 105 When processing a '.c' file, perf searches an installed LLVM to compile it 106 into an object file first. Optional clang options can be passed via the 107 '--clang-opt' command line option, e.g.: 108 109 perf record --clang-opt "-DLINUX_VERSION_CODE=0x50000" \ 110 -e tests/bpf-script-example.c 111 112 Note: '--clang-opt' must be placed before '--event/-e'. 113 114 - a group of events surrounded by a pair of brace ("{event1,event2,...}"). 115 Each event is separated by commas and the group should be quoted to 116 prevent the shell interpretation. You also need to use --group on 117 "perf report" to view group events together. 118 119--filter=<filter>:: 120 Event filter. This option should follow an event selector (-e) which 121 selects either tracepoint event(s) or a hardware trace PMU 122 (e.g. Intel PT or CoreSight). 123 124 - tracepoint filters 125 126 In the case of tracepoints, multiple '--filter' options are combined 127 using '&&'. 128 129 - address filters 130 131 A hardware trace PMU advertises its ability to accept a number of 132 address filters by specifying a non-zero value in 133 /sys/bus/event_source/devices/<pmu>/nr_addr_filters. 134 135 Address filters have the format: 136 137 filter|start|stop|tracestop <start> [/ <size>] [@<file name>] 138 139 Where: 140 - 'filter': defines a region that will be traced. 141 - 'start': defines an address at which tracing will begin. 142 - 'stop': defines an address at which tracing will stop. 143 - 'tracestop': defines a region in which tracing will stop. 144 145 <file name> is the name of the object file, <start> is the offset to the 146 code to trace in that file, and <size> is the size of the region to 147 trace. 'start' and 'stop' filters need not specify a <size>. 148 149 If no object file is specified then the kernel is assumed, in which case 150 the start address must be a current kernel memory address. 151 152 <start> can also be specified by providing the name of a symbol. If the 153 symbol name is not unique, it can be disambiguated by inserting #n where 154 'n' selects the n'th symbol in address order. Alternately #0, #g or #G 155 select only a global symbol. <size> can also be specified by providing 156 the name of a symbol, in which case the size is calculated to the end 157 of that symbol. For 'filter' and 'tracestop' filters, if <size> is 158 omitted and <start> is a symbol, then the size is calculated to the end 159 of that symbol. 160 161 If <size> is omitted and <start> is '*', then the start and size will 162 be calculated from the first and last symbols, i.e. to trace the whole 163 file. 164 165 If symbol names (or '*') are provided, they must be surrounded by white 166 space. 167 168 The filter passed to the kernel is not necessarily the same as entered. 169 To see the filter that is passed, use the -v option. 170 171 The kernel may not be able to configure a trace region if it is not 172 within a single mapping. MMAP events (or /proc/<pid>/maps) can be 173 examined to determine if that is a possibility. 174 175 Multiple filters can be separated with space or comma. 176 177--exclude-perf:: 178 Don't record events issued by perf itself. This option should follow 179 an event selector (-e) which selects tracepoint event(s). It adds a 180 filter expression 'common_pid != $PERFPID' to filters. If other 181 '--filter' exists, the new filter expression will be combined with 182 them by '&&'. 183 184-a:: 185--all-cpus:: 186 System-wide collection from all CPUs (default if no target is specified). 187 188-p:: 189--pid=:: 190 Record events on existing process ID (comma separated list). 191 192-t:: 193--tid=:: 194 Record events on existing thread ID (comma separated list). 195 This option also disables inheritance by default. Enable it by adding 196 --inherit. 197 198-u:: 199--uid=:: 200 Record events in threads owned by uid. Name or number. 201 202-r:: 203--realtime=:: 204 Collect data with this RT SCHED_FIFO priority. 205 206--no-buffering:: 207 Collect data without buffering. 208 209-c:: 210--count=:: 211 Event period to sample. 212 213-o:: 214--output=:: 215 Output file name. 216 217-i:: 218--no-inherit:: 219 Child tasks do not inherit counters. 220 221-F:: 222--freq=:: 223 Profile at this frequency. Use 'max' to use the currently maximum 224 allowed frequency, i.e. the value in the kernel.perf_event_max_sample_rate 225 sysctl. Will throttle down to the currently maximum allowed frequency. 226 See --strict-freq. 227 228--strict-freq:: 229 Fail if the specified frequency can't be used. 230 231-m:: 232--mmap-pages=:: 233 Number of mmap data pages (must be a power of two) or size 234 specification with appended unit character - B/K/M/G. The 235 size is rounded up to have nearest pages power of two value. 236 Also, by adding a comma, the number of mmap pages for AUX 237 area tracing can be specified. 238 239--group:: 240 Put all events in a single event group. This precedes the --event 241 option and remains only for backward compatibility. See --event. 242 243-g:: 244 Enables call-graph (stack chain/backtrace) recording for both 245 kernel space and user space. 246 247--call-graph:: 248 Setup and enable call-graph (stack chain/backtrace) recording, 249 implies -g. Default is "fp" (for user space). 250 251 The unwinding method used for kernel space is dependent on the 252 unwinder used by the active kernel configuration, i.e 253 CONFIG_UNWINDER_FRAME_POINTER (fp) or CONFIG_UNWINDER_ORC (orc) 254 255 Any option specified here controls the method used for user space. 256 257 Valid options are "fp" (frame pointer), "dwarf" (DWARF's CFI - 258 Call Frame Information) or "lbr" (Hardware Last Branch Record 259 facility). 260 261 In some systems, where binaries are build with gcc 262 --fomit-frame-pointer, using the "fp" method will produce bogus 263 call graphs, using "dwarf", if available (perf tools linked to 264 the libunwind or libdw library) should be used instead. 265 Using the "lbr" method doesn't require any compiler options. It 266 will produce call graphs from the hardware LBR registers. The 267 main limitation is that it is only available on new Intel 268 platforms, such as Haswell. It can only get user call chain. It 269 doesn't work with branch stack sampling at the same time. 270 271 When "dwarf" recording is used, perf also records (user) stack dump 272 when sampled. Default size of the stack dump is 8192 (bytes). 273 User can change the size by passing the size after comma like 274 "--call-graph dwarf,4096". 275 276-q:: 277--quiet:: 278 Don't print any message, useful for scripting. 279 280-v:: 281--verbose:: 282 Be more verbose (show counter open errors, etc). 283 284-s:: 285--stat:: 286 Record per-thread event counts. Use it with 'perf report -T' to see 287 the values. 288 289-d:: 290--data:: 291 Record the sample virtual addresses. 292 293--phys-data:: 294 Record the sample physical addresses. 295 296--data-page-size:: 297 Record the sampled data address data page size. 298 299--code-page-size:: 300 Record the sampled code address (ip) page size 301 302-T:: 303--timestamp:: 304 Record the sample timestamps. Use it with 'perf report -D' to see the 305 timestamps, for instance. 306 307-P:: 308--period:: 309 Record the sample period. 310 311--sample-cpu:: 312 Record the sample cpu. 313 314-n:: 315--no-samples:: 316 Don't sample. 317 318-R:: 319--raw-samples:: 320Collect raw sample records from all opened counters (default for tracepoint counters). 321 322-C:: 323--cpu:: 324Collect samples only on the list of CPUs provided. Multiple CPUs can be provided as a 325comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-2. 326In per-thread mode with inheritance mode on (default), samples are captured only when 327the thread executes on the designated CPUs. Default is to monitor all CPUs. 328 329-B:: 330--no-buildid:: 331Do not save the build ids of binaries in the perf.data files. This skips 332post processing after recording, which sometimes makes the final step in 333the recording process to take a long time, as it needs to process all 334events looking for mmap records. The downside is that it can misresolve 335symbols if the workload binaries used when recording get locally rebuilt 336or upgraded, because the only key available in this case is the 337pathname. You can also set the "record.build-id" config variable to 338'skip to have this behaviour permanently. 339 340-N:: 341--no-buildid-cache:: 342Do not update the buildid cache. This saves some overhead in situations 343where the information in the perf.data file (which includes buildids) 344is sufficient. You can also set the "record.build-id" config variable to 345'no-cache' to have the same effect. 346 347-G name,...:: 348--cgroup name,...:: 349monitor only in the container (cgroup) called "name". This option is available only 350in per-cpu mode. The cgroup filesystem must be mounted. All threads belonging to 351container "name" are monitored when they run on the monitored CPUs. Multiple cgroups 352can be provided. Each cgroup is applied to the corresponding event, i.e., first cgroup 353to first event, second cgroup to second event and so on. It is possible to provide 354an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must have 355corresponding events, i.e., they always refer to events defined earlier on the command 356line. If the user wants to track multiple events for a specific cgroup, the user can 357use '-e e1 -e e2 -G foo,foo' or just use '-e e1 -e e2 -G foo'. 358 359If wanting to monitor, say, 'cycles' for a cgroup and also for system wide, this 360command line can be used: 'perf stat -e cycles -G cgroup_name -a -e cycles'. 361 362-b:: 363--branch-any:: 364Enable taken branch stack sampling. Any type of taken branch may be sampled. 365This is a shortcut for --branch-filter any. See --branch-filter for more infos. 366 367-j:: 368--branch-filter:: 369Enable taken branch stack sampling. Each sample captures a series of consecutive 370taken branches. The number of branches captured with each sample depends on the 371underlying hardware, the type of branches of interest, and the executed code. 372It is possible to select the types of branches captured by enabling filters. The 373following filters are defined: 374 375 - any: any type of branches 376 - any_call: any function call or system call 377 - any_ret: any function return or system call return 378 - ind_call: any indirect branch 379 - call: direct calls, including far (to/from kernel) calls 380 - u: only when the branch target is at the user level 381 - k: only when the branch target is in the kernel 382 - hv: only when the target is at the hypervisor level 383 - in_tx: only when the target is in a hardware transaction 384 - no_tx: only when the target is not in a hardware transaction 385 - abort_tx: only when the target is a hardware transaction abort 386 - cond: conditional branches 387 - save_type: save branch type during sampling in case binary is not available later 388 389+ 390The option requires at least one branch type among any, any_call, any_ret, ind_call, cond. 391The privilege levels may be omitted, in which case, the privilege levels of the associated 392event are applied to the branch filter. Both kernel (k) and hypervisor (hv) privilege 393levels are subject to permissions. When sampling on multiple events, branch stack sampling 394is enabled for all the sampling events. The sampled branch type is the same for all events. 395The various filters must be specified as a comma separated list: --branch-filter any_ret,u,k 396Note that this feature may not be available on all processors. 397 398--weight:: 399Enable weightened sampling. An additional weight is recorded per sample and can be 400displayed with the weight and local_weight sort keys. This currently works for TSX 401abort events and some memory events in precise mode on modern Intel CPUs. 402 403--namespaces:: 404Record events of type PERF_RECORD_NAMESPACES. This enables 'cgroup_id' sort key. 405 406--all-cgroups:: 407Record events of type PERF_RECORD_CGROUP. This enables 'cgroup' sort key. 408 409--transaction:: 410Record transaction flags for transaction related events. 411 412--per-thread:: 413Use per-thread mmaps. By default per-cpu mmaps are created. This option 414overrides that and uses per-thread mmaps. A side-effect of that is that 415inheritance is automatically disabled. --per-thread is ignored with a warning 416if combined with -a or -C options. 417 418-D:: 419--delay=:: 420After starting the program, wait msecs before measuring (-1: start with events 421disabled). This is useful to filter out the startup phase of the program, which 422is often very different. 423 424-I:: 425--intr-regs:: 426Capture machine state (registers) at interrupt, i.e., on counter overflows for 427each sample. List of captured registers depends on the architecture. This option 428is off by default. It is possible to select the registers to sample using their 429symbolic names, e.g. on x86, ax, si. To list the available registers use 430--intr-regs=\?. To name registers, pass a comma separated list such as 431--intr-regs=ax,bx. The list of register is architecture dependent. 432 433--user-regs:: 434Similar to -I, but capture user registers at sample time. To list the available 435user registers use --user-regs=\?. 436 437--running-time:: 438Record running and enabled time for read events (:S) 439 440-k:: 441--clockid:: 442Sets the clock id to use for the various time fields in the perf_event_type 443records. See clock_gettime(). In particular CLOCK_MONOTONIC and 444CLOCK_MONOTONIC_RAW are supported, some events might also allow 445CLOCK_BOOTTIME, CLOCK_REALTIME and CLOCK_TAI. 446 447-S:: 448--snapshot:: 449Select AUX area tracing Snapshot Mode. This option is valid only with an 450AUX area tracing event. Optionally, certain snapshot capturing parameters 451can be specified in a string that follows this option: 452 'e': take one last snapshot on exit; guarantees that there is at least one 453 snapshot in the output file; 454 <size>: if the PMU supports this, specify the desired snapshot size. 455 456In Snapshot Mode trace data is captured only when signal SIGUSR2 is received 457and on exit if the above 'e' option is given. 458 459--aux-sample[=OPTIONS]:: 460Select AUX area sampling. At least one of the events selected by the -e option 461must be an AUX area event. Samples on other events will be created containing 462data from the AUX area. Optionally sample size may be specified, otherwise it 463defaults to 4KiB. 464 465--proc-map-timeout:: 466When processing pre-existing threads /proc/XXX/mmap, it may take a long time, 467because the file may be huge. A time out is needed in such cases. 468This option sets the time out limit. The default value is 500 ms. 469 470--switch-events:: 471Record context switch events i.e. events of type PERF_RECORD_SWITCH or 472PERF_RECORD_SWITCH_CPU_WIDE. In some cases (e.g. Intel PT, CoreSight or Arm SPE) 473switch events will be enabled automatically, which can be suppressed by 474by the option --no-switch-events. 475 476--clang-path=PATH:: 477Path to clang binary to use for compiling BPF scriptlets. 478(enabled when BPF support is on) 479 480--clang-opt=OPTIONS:: 481Options passed to clang when compiling BPF scriptlets. 482(enabled when BPF support is on) 483 484--vmlinux=PATH:: 485Specify vmlinux path which has debuginfo. 486(enabled when BPF prologue is on) 487 488--buildid-all:: 489Record build-id of all DSOs regardless whether it's actually hit or not. 490 491--buildid-mmap:: 492Record build ids in mmap2 events, disables build id cache (implies --no-buildid). 493 494--aio[=n]:: 495Use <n> control blocks in asynchronous (Posix AIO) trace writing mode (default: 1, max: 4). 496Asynchronous mode is supported only when linking Perf tool with libc library 497providing implementation for Posix AIO API. 498 499--affinity=mode:: 500Set affinity mask of trace reading thread according to the policy defined by 'mode' value: 501 node - thread affinity mask is set to NUMA node cpu mask of the processed mmap buffer 502 cpu - thread affinity mask is set to cpu of the processed mmap buffer 503 504--mmap-flush=number:: 505 506Specify minimal number of bytes that is extracted from mmap data pages and 507processed for output. One can specify the number using B/K/M/G suffixes. 508 509The maximal allowed value is a quarter of the size of mmaped data pages. 510 511The default option value is 1 byte which means that every time that the output 512writing thread finds some new data in the mmaped buffer the data is extracted, 513possibly compressed (-z) and written to the output, perf.data or pipe. 514 515Larger data chunks are compressed more effectively in comparison to smaller 516chunks so extraction of larger chunks from the mmap data pages is preferable 517from the perspective of output size reduction. 518 519Also at some cases executing less output write syscalls with bigger data size 520can take less time than executing more output write syscalls with smaller data 521size thus lowering runtime profiling overhead. 522 523-z:: 524--compression-level[=n]:: 525Produce compressed trace using specified level n (default: 1 - fastest compression, 52622 - smallest trace) 527 528--all-kernel:: 529Configure all used events to run in kernel space. 530 531--all-user:: 532Configure all used events to run in user space. 533 534--kernel-callchains:: 535Collect callchains only from kernel space. I.e. this option sets 536perf_event_attr.exclude_callchain_user to 1. 537 538--user-callchains:: 539Collect callchains only from user space. I.e. this option sets 540perf_event_attr.exclude_callchain_kernel to 1. 541 542Don't use both --kernel-callchains and --user-callchains at the same time or no 543callchains will be collected. 544 545--timestamp-filename 546Append timestamp to output file name. 547 548--timestamp-boundary:: 549Record timestamp boundary (time of first/last samples). 550 551--switch-output[=mode]:: 552Generate multiple perf.data files, timestamp prefixed, switching to a new one 553based on 'mode' value: 554 "signal" - when receiving a SIGUSR2 (default value) or 555 <size> - when reaching the size threshold, size is expected to 556 be a number with appended unit character - B/K/M/G 557 <time> - when reaching the time threshold, size is expected to 558 be a number with appended unit character - s/m/h/d 559 560 Note: the precision of the size threshold hugely depends 561 on your configuration - the number and size of your ring 562 buffers (-m). It is generally more precise for higher sizes 563 (like >5M), for lower values expect different sizes. 564 565A possible use case is to, given an external event, slice the perf.data file 566that gets then processed, possibly via a perf script, to decide if that 567particular perf.data snapshot should be kept or not. 568 569Implies --timestamp-filename, --no-buildid and --no-buildid-cache. 570The reason for the latter two is to reduce the data file switching 571overhead. You can still switch them on with: 572 573 --switch-output --no-no-buildid --no-no-buildid-cache 574 575--switch-output-event:: 576Events that will cause the switch of the perf.data file, auto-selecting 577--switch-output=signal, the results are similar as internally the side band 578thread will also send a SIGUSR2 to the main one. 579 580Uses the same syntax as --event, it will just not be recorded, serving only to 581switch the perf.data file as soon as the --switch-output event is processed by 582a separate sideband thread. 583 584This sideband thread is also used to other purposes, like processing the 585PERF_RECORD_BPF_EVENT records as they happen, asking the kernel for extra BPF 586information, etc. 587 588--switch-max-files=N:: 589 590When rotating perf.data with --switch-output, only keep N files. 591 592--dry-run:: 593Parse options then exit. --dry-run can be used to detect errors in cmdline 594options. 595 596'perf record --dry-run -e' can act as a BPF script compiler if llvm.dump-obj 597in config file is set to true. 598 599--synth=TYPE:: 600Collect and synthesize given type of events (comma separated). Note that 601this option controls the synthesis from the /proc filesystem which represent 602task status for pre-existing threads. 603 604Kernel (and some other) events are recorded regardless of the 605choice in this option. For example, --synth=no would have MMAP events for 606kernel and modules. 607 608Available types are: 609 'task' - synthesize FORK and COMM events for each task 610 'mmap' - synthesize MMAP events for each process (implies 'task') 611 'cgroup' - synthesize CGROUP events for each cgroup 612 'all' - synthesize all events (default) 613 'no' - do not synthesize any of the above events 614 615--tail-synthesize:: 616Instead of collecting non-sample events (for example, fork, comm, mmap) at 617the beginning of record, collect them during finalizing an output file. 618The collected non-sample events reflects the status of the system when 619record is finished. 620 621--overwrite:: 622Makes all events use an overwritable ring buffer. An overwritable ring 623buffer works like a flight recorder: when it gets full, the kernel will 624overwrite the oldest records, that thus will never make it to the 625perf.data file. 626 627When '--overwrite' and '--switch-output' are used perf records and drops 628events until it receives a signal, meaning that something unusual was 629detected that warrants taking a snapshot of the most current events, 630those fitting in the ring buffer at that moment. 631 632'overwrite' attribute can also be set or canceled for an event using 633config terms. For example: 'cycles/overwrite/' and 'instructions/no-overwrite/'. 634 635Implies --tail-synthesize. 636 637--kcore:: 638Make a copy of /proc/kcore and place it into a directory with the perf data file. 639 640--max-size=<size>:: 641Limit the sample data max size, <size> is expected to be a number with 642appended unit character - B/K/M/G 643 644--num-thread-synthesize:: 645 The number of threads to run when synthesizing events for existing processes. 646 By default, the number of threads equals 1. 647 648ifdef::HAVE_LIBPFM[] 649--pfm-events events:: 650Select a PMU event using libpfm4 syntax (see http://perfmon2.sf.net) 651including support for event filters. For example '--pfm-events 652inst_retired:any_p:u:c=1:i'. More than one event can be passed to the 653option using the comma separator. Hardware events and generic hardware 654events cannot be mixed together. The latter must be used with the -e 655option. The -e option and this one can be mixed and matched. Events 656can be grouped using the {} notation. 657endif::HAVE_LIBPFM[] 658 659--control=fifo:ctl-fifo[,ack-fifo]:: 660--control=fd:ctl-fd[,ack-fd]:: 661ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd as follows. 662Listen on ctl-fd descriptor for command to control measurement. 663 664Available commands: 665 'enable' : enable events 666 'disable' : disable events 667 'enable name' : enable event 'name' 668 'disable name' : disable event 'name' 669 'snapshot' : AUX area tracing snapshot). 670 'stop' : stop perf record 671 'ping' : ping 672 673 'evlist [-v|-g|-F] : display all events 674 -F Show just the sample frequency used for each event. 675 -v Show all fields. 676 -g Show event group information. 677 678Measurements can be started with events disabled using --delay=-1 option. Optionally 679send control command completion ('ack\n') to ack-fd descriptor to synchronize with the 680controlling process. Example of bash shell script to enable and disable events during 681measurements: 682 683 #!/bin/bash 684 685 ctl_dir=/tmp/ 686 687 ctl_fifo=${ctl_dir}perf_ctl.fifo 688 test -p ${ctl_fifo} && unlink ${ctl_fifo} 689 mkfifo ${ctl_fifo} 690 exec {ctl_fd}<>${ctl_fifo} 691 692 ctl_ack_fifo=${ctl_dir}perf_ctl_ack.fifo 693 test -p ${ctl_ack_fifo} && unlink ${ctl_ack_fifo} 694 mkfifo ${ctl_ack_fifo} 695 exec {ctl_fd_ack}<>${ctl_ack_fifo} 696 697 perf record -D -1 -e cpu-cycles -a \ 698 --control fd:${ctl_fd},${ctl_fd_ack} \ 699 -- sleep 30 & 700 perf_pid=$! 701 702 sleep 5 && echo 'enable' >&${ctl_fd} && read -u ${ctl_fd_ack} e1 && echo "enabled(${e1})" 703 sleep 10 && echo 'disable' >&${ctl_fd} && read -u ${ctl_fd_ack} d1 && echo "disabled(${d1})" 704 705 exec {ctl_fd_ack}>&- 706 unlink ${ctl_ack_fifo} 707 708 exec {ctl_fd}>&- 709 unlink ${ctl_fifo} 710 711 wait -n ${perf_pid} 712 exit $? 713 714include::intel-hybrid.txt[] 715 716SEE ALSO 717-------- 718linkperf:perf-stat[1], linkperf:perf-list[1], linkperf:perf-intel-pt[1] 719